REPORT abc.

DATA : BEGIN OF itab OCCURS 0,
num TYPE i,
END OF itab.
data : std type p decimals 2.

*-------------------------------------------------

itab-num = 8. APPEND itab.
itab-num = 25. APPEND itab.
itab-num = 7. APPEND itab.
itab-num = 5. APPEND itab.

itab-num = 8. APPEND itab.
itab-num = 3. APPEND itab.
itab-num = 10. APPEND itab.
itab-num = 12. APPEND itab.
itab-num = 9. APPEND itab.

PERFORM stdev changing std..

write :/ std.

*-------------------------------------------------

*-------------------------------------------------
*
*-------------------------------------------------

FORM stdev CHANGING std.

DATA : mn TYPE p DECIMALS 2.
DATA : sm TYPE i.
DATA : sm2 TYPE i.
DATA : dev TYPE p DECIMALS 2.

DATA : cnt TYPE i.

LOOP AT itab.
sm = sm + itab-num.
cnt = cnt + 1.
sm2 = sm2 + ( itab-num * itab-num ).
ENDLOOP.

mn = sm / cnt.

dev = ( sm2 - ( ( ( sm * sm ) / cnt ) ) ) / ( cnt - 1 ) .
dev = SQRT( dev ).

std = dev.

ENDFORM. "stdev